Metallic fission product retention of coated particles with ceramic kernel additives

The retention of metallic fission products in coated particles with ceramic kernel additives is studied out-of-pile and in-pile. The ceramic additives are easily introduced without any significant change of kernel fabrication processes. The excellent efficiency of alumina-silica kernel additives for retaining 90Sr and 140Ba is demonstrated in-pile. The fractional release is reduced by two orders of magnitude. Silver-110m is not retained by the kernel additives. Cesium forms compounds in the alumina-silica additives, which become unstable at temperatures above 14000C (1673 K). At normal high-temperature gas-cooled reactor operation temperatures [1000 to 12000C (1273 to 1473 K)], the diffusion coefficient of cesium in oxide kernels with alumina-silica additives is reduced by about two orders of magnitude